Published 9:54 am, Thursday, February 13, 2014

DEAR DOCTOR K: My neighbor was diagnosed with Lyme disease. Why does he still have symptoms, even though he has completed his treatment?

DEAR READER: The great majority of people diagnosed with Lyme disease, and properly treated, are cured. However, there are some people like your neighbor, who are never fully cured, and we do not understand why proper diagnosis and treatment does not always lead to the elimination of suffering.

Here’s what we do know. Lyme disease is an infection caused by bacteria that are transmitted through tick bites. The first symptom is usually a flat, reddish rash that spreads from the site of the tick bite. It often develops a central clear area known as a bull’s-eye. (I’ve put an illustration of this characteristic rash on my website, AskDoctorK.com.)

Over several days to weeks after the tick bite, the bacteria spread from the skin where the tick bite occurred. They can spread to the brain and heart, causing neurological problems and an inflammation of the heart muscle. Treatment involves a several-week course of antibiotics either taken by mouth or given intravenously (into a vein).

There are some important things to note about Lyme disease and treatment:

• It is possible to have Lyme disease more than once.

• Some people with Lyme disease need more than one course of treatment before they are cured.

• Occasionally, people with Lyme disease can be cured of the infection, but then develop “reactive arthritis.” This is a condition in which the bacteria that caused the Lyme disease trigger an immune attack on the joints.

• The ticks that carry the Lyme disease bacteria also can carry other types of bacteria that produce some symptoms similar to Lyme disease. Those other bacteria may not be killed as effectively by the antibiotics used to treat Lyme disease.

• Some people experience symptoms, such as fatigue or difficulty concentrating, after the infection is treated. This may happen even when there is no evidence that the bacteria are still in the body.

People who, like your neighbor, continue to have symptoms after what is thought to be proper treatment are sometimes given the diagnosis of “chronic Lyme disease.” This diagnosis is controversial, as the term implies that the persistent symptoms are caused by an ongoing infection with Lyme disease bacteria.

Most Lyme disease experts believe this happens only rarely (or never). But some doctors diagnose chronic Lyme disease frequently and prescribe long-term intravenous antibiotics. In my opinion, the evidence that such long-term treatment helps is not very strong.

But I also believe we don’t understand enough about this condition for anyone to hold strong opinions. I also don’t believe that such patients are just “imagining” that they are sick. Something — Lyme bacteria, other bacteria or viruses, or an unusual response of their immune system to infection — is making them sick. We just haven’t figured out what it is.

Dr. Komaroff is a physician and professor at Harvard Medical School. AskDoctorK.com